Evergreen shrub with upright stem (8)
I believe the answer is:
standard
'stem' is the definition.
(thesaurus)
'evergreen shrub with upright' is the wordplay.
I cannot really see how this works, but
'with' could be 'and' and 'and' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for standard that I've seen before include "Flag; criterion" , "'Reference point, touchstone (8)'" , "Basic criterion" , "Ordinary Level?" , "Touchstone, benchmark 98)" .)